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Journal of Foot and Ankle Research
Open Access
Research
Hydrodebridement of wounds: effectiveness in reducing wound
bacterial contamination and potential for air bacterial
contamination
Frank L Bowling*
1
, Daryl S Stickings
2
, Valerie Edwards-Jones
3
,
David G Armstrong
1,4
and Andrew JM Boulton
1
Address:
1
Department of Medicine Manchester Royal Infirmary, University of Manchester, Manchester, UK,
2
Manchester Foot Clinic, Manchester
Community Health, Manchester, UK,
3
Department of Clinical Microbiology, Manchester Metropolitan University, Manchester, UK and
4
Department of Surgery, University of Arizona College of Medicine, Tucson, AZ, USA
Email: Frank L Bowling* - ; Daryl S Stickings - ; Valerie Edwards-

Jones - ; David G Armstrong - ; Andrew JM Boulton -
* Corresponding author
Abstract
Background: The purpose of this study was to assess the level of air contamination with bacteria
after surgical hydrodebridement and to determine the effectiveness of hydro surgery on bacterial
reduction of a simulated infected wound.
Methods: Four porcine samples were scored then infected with a broth culture containing a
variety of organisms and incubated at 37°C for 24 hours. The infected samples were then debrided
with the hydro surgery tool (Versajet, Smith and Nephew, Largo, Florida, USA). Samples were
taken for microbiology, histology and scanning electron microscopy pre-infection, post infection
and post debridement. Air bacterial contamination was evaluated before, during and after
debridement by using active and passive methods; for active sampling the SAS-Super 90 air sampler
was used, for passive sampling settle plates were located at set distances around the clinic room.
Results: There was no statistically significant reduction in bacterial contamination of the porcine
samples post hydrodebridement. Analysis of the passive sampling showed a significant (p < 0.001)
increase in microbial counts post hydrodebridement. Levels ranging from 950 colony forming units
per meter cubed (CFUs/m
3
) to 16780 CFUs/m
3
were observed with active sampling of the air whilst
using hydro surgery equipment compared with a basal count of 582 CFUs/m
3
. During removal of
the wound dressing, a significant increase was observed relative to basal counts (p < 0.05).
Microbial load of the air samples was still significantly raised 1 hour post-therapy.
Conclusion: The results suggest a significant increase in bacterial air contamination both by active
sampling and passive sampling. We believe that action might be taken to mitigate fallout in the
settings in which this technique is used.
Published: 8 May 2009

Journal of Foot and Ankle Research 2009, 2:13 doi:10.1186/1757-1146-2-13
Received: 4 November 2008
Accepted: 8 May 2009
This article is available from: />© 2009 Bowling et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( />),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Journal of Foot and Ankle Research 2009, 2:13 />Page 2 of 8
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Background
Treatment of chronic wounds frequently requires a com-
bination of medical and surgical therapy to effect success-
ful healing. Non-viable tissue may serve as a source of
infection and thereby retard wound healing or increase
the risk for complications [1-3]. Therefore by removing
necrotic tissue and reducing the bacterial load on the
wound surface, wound debridement may assist in healing
[4,5].
There are numerous wound debridement techniques
available to the clinician [6]. Surgical (also known as
sharp) debridement using a scalpel or a biopsy is consid-
ered the optimal method for rapidly cleaning the ulcer
and converting it to an acute wound; however it can be
painful and not all practitioners are trained or permitted
to perform such procedures. Other mechanical forms of
"sharp" debridement include pulsed lavage, ultrasound
disruption of debris, and high-pressure water jet dissec-
tion of the wound surface [7]. These alternative tech-
niques may possibly serve to reduce biofilm prevalence
and local bacterial burden thereby stimulating the repair
process. Additionally, they may be better able to debride

superficial slough than traditional biopsy or scalpels.
Over the past several years, these alternate mechanical
methods of debridement have become increasingly com-
monplace both in operating rooms and in clinical settings
worldwide and are generally well regarded by clinicians
that employ them. We are, however, unaware of prior
reports that have evaluated the potential for aerosoliza-
tion of particulates, namely bacteria, into the peri-opera-
tive environment whist using these modalities.
The purpose of this study was therefore to evaluate the
potential for aerosolization of microbes during hydrode-
bridement therapy and additionally determine the effec-
tiveness of hydro surgery in reducing the amount of
bacteria in a simulated infected wound.
Method
Four porcine joints with skin intact were purchased on
day 1 of the study and disinfected with 90% alcohol. Arti-
ficial wounds were created with a scalpel blade to produce
three wound sites per specimen; a superficial wound (site
1), a deep wound without a sinus (site 2) and a deep
wound with a sinus (site 3).
Baseline sampling
Biopsies were taken from site 1 of each porcine specimen
using a 6 mm sterile cutter. Samples were collected in nor-
mal saline for histology and scanning electron microscopy
(SEM). Three swabs were taken from each site of each
specimen.
Swabs were immersed in 1 ml of phosphate buffered
saline (PBS) and vortex mixed to promote equal bacterial
suspension. 0.1 ml of suspension was removed and added

to 9.9 ml of PBS to produce a 10'2 dilution. Culture plates
were inoculated with 50 ul using a Spiral Plater. Mannitol
salt agar was used for detection and enumeration of Sta-
phylococcus aureus, Nutrient Agar for Pseudomonas aerugi-
nosa and MacConkey Agar for Escherichia coli. Plates were
incubated for 24 hours at 37 degrees centigrade after
which further dilution was achieved by adding 0.1 ml of
the incubated sample to 9.9 ml PBS for 10'4 dilution.
Plates were again inoculated and incubated as above. The
resulting CFUs were counted using an image analyser.
Biopsies taken for microbiology were placed in 1 ml of
PBS and weighed then vortex mixed. The contents were
ground in a sterile grinder until the tissue was evenly
homogenised then transferred to a sterile universal con-
tainer for five minutes of further vortex mixing. This was
then processed as for the swabs.
Biopsies for electron microscopy were fixed in 10% neu-
tral buffered formalin for 48 hours to kill any bacteria. The
formalin was removed by washing in distilled water then
passing through various concentrations of alcohol to
remove residual water before allowing drying. Gold was
used as a sputter coating before being mounted for view-
ing on the SEM.
Specimen inoculation
On completion of baseline sampling the artificial wounds
on each of the four specimens were inoculated with vari-
ous pathogens. Specimen 1 was infected with Oxford Sta-
phylococcus aureus, specimen 2 with Pseudomonas
aeruginosa, specimen 3 with Escherichia coli. Specimen 4
was infected with 1 ml of an overnight polymicrobial

broth culture derived from a patient with a Methicillin-
resistant Staphylococcus aureus colonised wound. The spec-
imens were then incubated in a sterile container overnight
at 37°c. Swab and biopsy samples were taken after incu-
bation and again following debridement using the same
method described for baseline sampling.
Hydrodebridement
All specimens were debrided consecutively on the same
day and in the same treatment room. The room was
approximately 3 metres by 5 metres in size and represent-
ative of a typical outpatient clinic. In keeping with operat-
ing room requirements there was no controlled air flow.
The clinical room was disinfected after each debridement
and a two hour rest period followed when the proceeding
treatment was a different specimen. This approach was in
accordance with local infection control policy to allow for
dispersal of any pathogens [8].
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The Versajet operator had undergone training in the the-
ory and practise of the Versajet in a clinical setting. During
debridement the operator wore gloves, plastic apron, bon-
net, visor and mask for protection against contamination
and injury.
Evaluation of air bacterial contamination: active sampling
Air sampling took place at three stages in the treatment
process using the SAS-Super 90 air sampler (SAS). One
hour before debridement the air was tested to provide
baseline data. Specimens were presented for treatment
with a dressing over the artificial wound which was

removed immediately prior to debridement using a sterile
non touch technique during which another air sample
was taken. This was representative of clinical treatment
sessions allowing for the possibility of aerosolisation of
bacteria from the wound.
Specimens were debrided until "surgically" clean which
took approximately five minutes to complete for the three
sites on each specimen. During the procedure the air was
sampled at 100 litres per minute on the right hand side of
the Versajet operator. The SAS was positioned 2.5 metres
from the operator at head height. Further 1 minute sam-
ples were collected following treatment completion after
5, 15, 30 and 60 minutes. All samples were analysed for
microbial content.
Evaluation of air bacterial content: passive sampling
In order to sample the air by passive methods 12 settle
plates were situated around the sampling area. Figure 1 is
a schematic diagram (plan view) of the treatment room
layout illustrating the position of Versajet, settle plates
and the SAS. Settle plates contained Tryptone soya agar
(TSA) and were placed on the floor at 1, 2 and 3 metres
from the active sampling area. Plates were 90 mm diame-
ter. Settle plates were positioned 5 minutes after the
removal of the dressing procedure, and then remained in
situ for the 5 minute hydro surgery debridement and the
subsequent 55 minutes. This made a total collection time
for the settle plates of 1 hour. The settle plates were
replaced prior to each new sample debridement.
Table 1: Mean bacterial count pre-versajet and post-versajet.
Site 1 Site 2 Site 3

Swab CFUs/ml Swab CFUs/ml Swab CFUs/ml Biopsy CFUs/ml
Specimen 1 (Staphylococcus aureus)
Pre-Versajet 5.57 × 10
8
2.57 × 10
8
3.53 × 10
8
4.43 × 10
7
Post-Versajet 9.03 × 10
8
7.97 × 10
6
2.65 × 10
7
2.13 × 10
6
Specimen 2 (Pseudomonas aeruginosa)
Pre-Versajet 5.54 × 10
7
2.12 10
8
7.68 × 10
7
5.60 × 10
7
Post-Versajet 5.38 × 10
7
3.17 × 10

8
3.07 × 10
8
8.20 × 10
6
Specimen 3 (Escherichia coli)
Pre-Versajet 1.10 × 10
8
1.57 × 10
8
4.00 × 10
7
3.00 × 10
7
Post-Versajet 3.20 × 10
6
6.47 × 10
6
5.20 × 10
6
5.67 × 10
6
Specimen 4 (Mixed wound organisms)
Pre-Versajet 1.17 × 10
7
7.70 × 10
6
4.57 × 10
6
4.74 × 10

6
Post-Versajet N/A 2.43 × 10
6
1.73 × 10
6
4.07 × 10
6
Note: site 1 = Small deep cut, site 2 = small deep cut with a sinus, site 3 = a superficial wound, N/A – not available.
Schematic diagram (plan view) of the treatment room layout illustrating position of Versajet, settle plates and SAS-Super 90 air sampler (not to scale)Figure 1
Schematic diagram (plan view) of the treatment
room layout illustrating position of Versajet, settle
plates and SAS-Super 90 air sampler (not to scale).
3m
5m
VersaJet
Console
and
O
p
erator
1m
2m
3m
SAS
Settle
Plates
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Statistical analysis was by Minitab v15 (Minitab Inc., State
College PA, USA). Significance testing on this parametric

data was performed with t-tests.
Results
Microbiology
No surface contaminating organisms were identified from
the pre-inoculation sampling. Following debridement
with the Versajet all wound sites in all specimens
appeared clean and free from visible signs of infection.
Bacterial counts obtained from specimens before and after
Versajet treatment showed no significant difference. Five
of the twelve swab samples (42%) showed a non-signifi-
cant reduction in bacteria with a 1–1.5 log reduction in
the post debridement bacterial count. The biopsy samples
yielded up to 1 log reduction in bacterial counts with the
Escherichia coli specimens showing the greatest decrease
(Table 1). Wound type did not have an affect on bacterial
numbers obtained pre and post treatment. Figure 2 illus-
trates Staphylococcus aureus counts from specimen 1 pre
and post Versajet for all three wound sites.
Table 2: Results of active sampling: number of colony forming units (CFUs) during each minute of the debridement process.
CFUs/100 litres of air Bacteria isolated
Specimen 1 Staphylococcus aureus
I min 23 No SA
2 min 72 50 SA
3 min TNTC**** SA +++
4 min TNTC**** SA+++
Specimen 2 Pseudomonas aeruginosa
I min 10 1 SA
2 min 36 5 SA
3 min 20 1 SA, 2 PAE
4 min 9 2 SA, 5 PAE

Specimen 3 Escherichia coli
I min 9
2 min 9
3 min 15
4 min 10 2 ECO
Specimen 4 Mixed wound bacteria
I min 4 4 MRSA
2 min 0
3 min 0
4 min 7
Note: **** = Versajet blocked SA = Staphylococcus aureus; PAE = Pseudomonas aeruginosa; ECO = Escherichia coli; MRSA = Methicillin-resistant
Staphylococcus aureus; TNTC = To numerous to count.
This figure shows the Staphylococcus aureus count from speci-men 1Figure 2
This figure shows the Staphylococcus aureus count
from specimen 1. The top row shows pre-Versajet Staphy-
lococcus aureus counts from the three sites and the lower
row is the post Versajet.
Journal of Foot and Ankle Research 2009, 2:13 />Page 5 of 8
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Results for active air sampling
During the actual debridement process the infecting
organisms were isolated from the air and in the case of
specimen 2 air samples contained Staphylococcus aureus
from the previous debridement (Table 2). Figure 3 illus-
trates Pseudomonas aeruginosa isolated from active sam-
pling during Versajet use. Microbial count levels ranged
from 950 CFUs/m3 to 16780 CFUs/m3 during treatment.
The mean bacterial counts for all samples per minute are
shown in Table 3. Although counts decreased after treat-
ment cessation the microbial load of air samples was still

significantly raised one hour post therapy at 850 CFUs/
m3 (Figure 4) compared to background levels. Air sam-
ples taken during dressing removal showed a significant
increase (p < 0.05) in microbial counts relative to baseline
(Table 3).
Results from passive air sampling
The results from the settle plates showed a higher number
of CFUs in the 1 m and 2 m zones when compared to the
3 m zone (Table 4). During debridement of specimen 1
the Versajet became temporarily blocked and there was a
large increase in CFUs on the settle plates to the extent
that they were too numerous to count. This is shown in
Figure 5. Figure 6 shows the settle plate bacteria from the
left side of the peri-operative environment up to 3 metres
away from the treatment trolley. The high number of
CFUs is visible to the naked eye. Results from electron
microscopy showed adhesion of bacteria to the specimen
surfaces. Figure 7 illustrates Methicillin-resistant Staphylo-
coccus aureus.
Discussion
There is substantial empirical evidence that wound heal-
ing can be improved with surgical debridement and a gen-
eral consensus among clinicians that debridement creates
a favourable wound bed [4-6]. Positive outcomes reported
include an increase in the percentage of granulation tissue
and a marked decrease in slough.
One aim of this study was to examine bacterial load fol-
lowing hydro surgery debridement. No significant differ-
ences were found between bacterial counts of wound
swabs or biopsies obtained pre and post hydro surgery

independent of bacteria or wound type. Although wounds
had an improved appearance after treatment there was no
significant reduction in bacterial load.
However, it is clear from the CFUs illustrated in Figure 2
that hydro surgery can decrease the quantity of bacteria
resident in a wound to some extent but not reaching sig-
nificance. One wound site actually saw an increase in bac-
terial count post debridement. This occurred in a site
designed to simulate a deep wound with a sinus. We sug-
gest that this could be due to inaccuracies arising from the
use of swabs to collect material from a deep seated, irreg-
ular and undermined wound with a sinus.
Despite not achieving statistical significance the results
still demonstrate a decrease in the quantity of bacteria
present in the wound but the question of where the organ-
isms go needs to be addressed. Tables 2 and 4 provide evi-
dence of aerosolization of bacteria both during and
Shows the air sampling during debridement using Versajet on specimen infected with Pseudomonas aeruginosaFigure 3
Shows the air sampling during debridement using
Versajet on specimen infected with Pseudomonas aer-
uginosa.
Table 3: Results of active sampling: mean bacterial count by active sampling during dressing removal of each sample and for each
minute of debridement of the four samples.
Sample Remove Dressing (CFUs/m
3
) Minute During Versajet (CFUs/m
3
)
1 1415 1 775
2 1290 2 1440

3 1205 3 2115
4 1520 4 5335
Journal of Foot and Ankle Research 2009, 2:13 />Page 6 of 8
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following debridement. Furthermore, this fallout appears
to be displaced throughout much of the peri-operative
environment as illustrated by Figure 6.
Of grave concern are the extreme bacterial quantities
recorded when the debridement tool becomes blocked as
seen in Figure 5. Our results showed irregular displace-
ment of pathogens especially in the front right settle
plates. The only area to avoid significant fallout was 3
meters in front and to the right of the clinician. It is not
possible to account for equal or unequal fallout, due to
the nature of high pressure spray but we can postulate that
the SAS may have obscured the front right 3 meter settle
plate.
During the active sampling process a count of 16780
CFUs/m
3
was obtained which is extremely high. A possi-
ble explanation would be that the CFUs visible during
imaging had originated from more than one cell thus
when the plate becomes crowded the actual number of
visible CFUs does not represent a true figure. A statistical
factor has been applied to allow for this hence a higher
value is obtained.
Despite a two-hour time delay between debridement of
different specimens cross contamination occurred (Table
2). The samples taken from specimen two, inoculated

with Pseudomonas aeruginosa, also contained Staphylococcus
aureus from the previous specimen.
Our results clearly demonstrate that there is a potentially
high risk of contaminating the peri-operative environ-
ment during the process of hydrodebridement making
cross infection a real possibility. Careful consideration of
Table 4: Results from passive sampling: average bacterial counts at each settle plate location for all samples collected over a 1 hour
period.
Settle plates (back right) Settle plates (front right) Settle plates (back left) Settle plates (front left)
1 m 85 *** 45 80 180**
2 m 46*** 106** 80 47
3 m 44 0 72 32
Note: *** colonies include Staphylococcus aureus and Escherichia coli ** predominantly Pseudomonas aeruginosa
The aerosolization effect of Versajet therapy pre, during and post Versajet debridement and dressing removalFigure 4
The aerosolization effect of Versajet therapy pre, during and post Versajet debridement and dressing removal.
0
1000
2000
3000
4000
5000
6000
1
h
ou
r
Pr
e
Ve
r

s
a
j
et (
CFUs
/
m
3)
Remove Dressing (CFUs/m3)
Dur
i
n
g
Ve
r
saj
e
t
1
st
m
i
nu
te
(
CFUs
/
m
3)
D

u
ring Versajet 2nd minute (CFUs/m3)
Dur
i
n
g
Ve
r
saj
e
t
3
r
d
m
i
nu
te
(
CFU
s/
m
3
)
During Versajet 4th m
i
nu
t
e (CFUs/m3
)

5

min Po
s
t Ve
r
saj
e
t
(
CFUs/
m
3
)
1
5
m
i
n P
o
st Versaj et

(CFUs
/
m3)
30

min Po
s
t Ve

r
saj
e
t
(
CFUs/ m 3
)
6
0
m
i
n
Po
st Vers
a
je
t
(CFUs
/
m
3
)
Microbial Load (CFUs/ m3)
Journal of Foot and Ankle Research 2009, 2:13 />Page 7 of 8
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clinical location is necessary prior to using such debride-
ment tools, particularly as hydro-surgery consoles are
becoming increasingly used in community clinic settings
globally. This is especially true in a climate where hospital
acquired infections are under increasing scrutiny. The fall-

out recorded from dressing removal deserves the same
consideration independent of hydro surgery and has
implications for clinicians on a daily basis at every level.
The results from this study should not dissuade the clini-
cian from utilising hydro surgery as an adjunct to other
treatments but it is vital that action be taken to mitigate
the bacterial fallout associated with its use. A transparent
hood to cover the cutting tool and seal the affected area
may reduce potential fallout, thus reducing bacterial con-
tamination. Similarly, an improved cutting tool designed
with bacterial fallout in mind could diminish contamina-
tion.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
FLB and VEJ conceived and designed the study. DSS and
DGA conducted the statistical analysis. FLB and DSS com-
piled the data and drafted the manuscript and AJMB con-
tributed to the drafting of the manuscript. All authors read
and approved the final manuscript.
Acknowledgements
We have not received any financial support for the study. We would like
to acknowledge the staff within the Department of Clinical Microbiology,
Manchester Metropolitan University for their time and effort.
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